20,833 research outputs found
The hybrid SZ power spectrum: Combining cluster counts and SZ fluctuations to probe gas physics
Sunyaev-Zeldovich (SZ) effect from a cosmological distribution of clusters
carry information on the underlying cosmology as well as the cluster gas
physics. In order to study either cosmology or clusters one needs to break the
degeneracies between the two. We present a toy model showing how complementary
informations from SZ power spectrum and the SZ flux counts, both obtained from
upcoming SZ cluster surveys, can be used to mitigate the strong cosmological
influence (especially that of sigma_8) on the SZ fluctuations. Once the strong
dependence of the cluster SZ power spectrum on sigma_8 is diluted, the cluster
power spectrum can be used as a tool in studying cluster gas structure and
evolution. The method relies on the ability to write the Poisson contribution
to the SZ power spectrum in terms the observed SZ flux counts. We test the toy
model by applying the idea to simulations of SZ surveys.Comment: 12 pages. 11 plots. MNRAS submitte
Extragalactic millimeter-wave point source catalog, number counts and statistics from 771 square degrees of the SPT-SZ Survey
We present a point source catalog from 771 square degrees of the South Pole
Telescope Sunyaev Zel'dovich (SPT-SZ) survey at 95, 150, and 220 GHz. We detect
1545 sources above 4.5 sigma significance in at least one band. Based on their
relative brightness between survey bands, we classify the sources into two
populations, one dominated by synchrotron emission from active galactic nuclei,
and one dominated by thermal emission from dust-enshrouded star-forming
galaxies. We find 1238 synchrotron and 307 dusty sources. We cross-match all
sources against external catalogs and find 189 unidentified synchrotron sources
and 189 unidentified dusty sources. The dusty sources without counterparts are
good candidates for high-redshift, strongly lensed submillimeter galaxies. We
derive number counts for each population from 1 Jy down to roughly 9, 5, and 11
mJy at 95, 150, and 220 GHz. We compare these counts with galaxy population
models and find that none of the models we consider for either population
provide a good fit to the measured counts in all three bands. The disparities
imply that these measurements will be an important input to the next generation
of millimeter-wave extragalactic source population models.Comment: 23 pages, 8 figures, submitted to Ap
Lossy Compression with Privacy Constraints: Optimality of Polar Codes
A lossy source coding problem with privacy constraint is studied in which two
correlated discrete sources and are compressed into a reconstruction
with some prescribed distortion . In addition, a privacy
constraint is specified as the equivocation between the lossy reconstruction
and . This models the situation where a certain amount of source
information from one user is provided as utility (given by the fidelity of its
reconstruction) to another user or the public, while some other correlated part
of the source information must be kept private. In this work, we show that
polar codes are able, possibly with the aid of time sharing, to achieve any
point in the optimal rate-distortion-equivocation region identified by
Yamamoto, thus providing a constructive scheme that obtains the optimal
tradeoff between utility and privacy in this framework.Comment: Submitted for publicatio
Source Galerkin Calculations in Scalar Field Theory
In this paper, we extend previous work on scalar theory using the
Source Galerkin method. This approach is based on finding solutions to
the lattice functional equations for field theories in the presence of an
external source . Using polynomial expansions for the generating functional
, we calculate propagators and mass-gaps for a number of systems. These
calculations are straightforward to perform and are executed rapidly compared
to Monte Carlo. The bulk of the computation involves a single matrix inversion.
The use of polynomial expansions illustrates in a clear and simple way the
ideas of the Source Galerkin method. But at the same time, this choice has
serious limitations. Even after exploiting symmetries, the size of calculations
become prohibitive except for small systems. The calculations in this paper
were made on a workstation of modest power using a fourth order polynomial
expansion for lattices of size ,, in , , and . In
addition, we present an alternative to the Galerkin procedure that results in
sparse matrices to invert.Comment: 31 pages, latex, figures separat
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